The present invention relates to a self-containing full-complement roller bearing cage.
A self-containing cage for a rotative roller bearing is known, which has two side plates fastened to each other by means of bolts and which contains cylindrical rollers, the ends of which penetrate at either side into a deepening of an adjacent side plate (U.S. Pat. No. 502,025). At this known cage the bolts are placed between the rollers, so that neighbored rollers have a relatively large distance between each other around the circumference, thus only a relatively small number of rollers can be built into the bearing which often causes a too small load carrying capacity of the bearing per unit length of raceway.
Another self-containing cage for a rotative roller bearing is known, which has hollow cylindrical rollers, each roller having a through-going central hole, whereby a bolt penetrates axially through each hole and both ends of each bolt are rigidly fastened onto a side plate at the corresponding side of the cage (U.S. Pat. No. 236,517). This other known cage can be made as a full-complement unit, so that it contains an optimal large number of rollers on its circumference. However, an important disadvantage is to be seen in the fact, that every roller must be slidingly held and centered on its bolt during bearing operation. The contacting sliding surfaces between roller and bolt are difficult to maintain continuously lubricated with the indispensable lubricant, grease or oil, because in case the flowing lubricating medium is placed between the hole and the bolt it will be flung out of the bore of the rotating roller by the effect of centrifugal force, the medium flings radially outwardly, thereby being taken away from the sliding surfaces of the bore of the roller, where it is intended to lubricate and to protect against sliding wear. Therefore, in this other known cage there can develop easily a detrimental sliding wear in the bore between roller and bolt, which makes the sliding gap between the rollers and the bolt growing larger. The rollers of the cage then begin to inadmissibly oscillate during operation and to run obliquely. This again adds to the wear in the roller bores, thus this wear becomes greater and increases faster. Especially during running with high bearing load, there is produced an additional parasitical contact wear on the raceways of the roller bearing, because the obliquely running rollers do not roll properly on their raceways. In some cases where the oblique position of the rollers in the known cage has become great enough, these rollers may even produce a catastrophical blockade of the bearing during operation.
One object of the present invention is therefore to establish a self-containing full-complement bearing of the defined kind, in which the sliding wear in the flow medium lubricated cage is considerably reduced, in as much as a detrimental greater oblique position of the rollers in the cage is avoided even during long operation time and heavy bearing load.
A further object of the present invention is to provide a cage which can be manufactured extremely economically by using simple manufacturing means.
With the cage of this invention both ends of the cylindrical long-rollers of the cage are in part embraced on their outer surface by part-cylindrical guiding surfaces of recesses in the side plates of the cage, whereby the long rollers are properly, i.e. without obliquity, held by the narrowly guiding surfaces in the recesses. In addition the cage is carried by said guiding surfaces on the outer surface of the long rollers in the roller bearing. During operation of the bearing equipped with said cage, part of the ambient lubricant in the axial bore of the short-rollers becomes centrifugally pushed towards the side ends of the short-rollers and from there it is flung radially outwardly towards the outer surface of the adjacent long rollers. In this way there is effected a continuous distribution of flowing lubricating medium environment, for instance of an oil bath, both to the outer surface of the long rollers and to the guiding surfaces of the recesses of the side plates, which closely slide on this outer surface.
The cylindrical outer surface of each short-roller can slidingly contact the cylindrical outer surface of the neighboring long-roller, when during operation of the roller bearing a small, constructively defined running play between these two rollers is overcome. After the running through of this play, these two rollers slightly impact each other on their mutual cylindrical outer surfaces, this impact producing an alignment of the short rollers on the long-rollers. The mass inertia forces of the mutual impact are rather small, because the short-rollers have a relatively small mass, which is smaller than the mass of the long-roller.
Even during long-time operation with high bearing load the magnitude of the running play between the outer surfaces of adjacent long-roller and short-roller does not change, this is because of the relatively small mass forces and because of continuous distribution of the lubricating medium into the contacting outer surfaces, which makes the mutual impact and corresponding sliding wear on these surfaces to be of negligible importance.
The long-rollers of the cage are closely held and slidingly guided in the recesses of the two side-plates, which are positioned against each other by bolts, so that the long-rollers can not fall out of the cage. The central bore of each short roller is passed through axially by one bolt. By this way, each short-roller is held in the non-mounted cage by its bolt and restrained from falling out of the loose cage. The cage of this invention, therefore, forms a self-containing machine element, which can easily be mounted and dismounted, for instance, when the raceways of the roller bearing have to be inspected after a certain running period of the roller bearing.
Moreover, the cage of this invention has a full complement of rollers, so that an exceptionally high number of rollers per unit raceway length participate to carry the bearing load. This brings about the fact, that a roller bearing, which is equipped with the cage of this invention has a relatively high bearing capacity.
A second embodiment of this invention has the effect, that there is an extremely and unusually small play between the cylindrical outer surfaces of long-roller and adjacent short-roller in the cage, so that an optimally high number of rollers per unit raceway length is present. The mass forces during the mutual impacts between long-roller and short-roller are concomitantly kept advantageously small because of this very small play.
In a third embodiment, the long-rollers of the cage has an optimally narrow sliding gap in the pertinent recesses of the side plates at their both ends. This produces the advantage, that each long-roller is freely rotative and, thereby, guided in those recesses without obliquity.
In a fourth embodiment, both ends of the long-rollers are slidingly contacted and guided by sufficiently wide surface sections of the guiding surfaces of the side plates"" recesses. Thereby, an unacceptably high contact pressure force and a corresponding detrimental contact wear on these surface sections is avoided during bearing operation.
In a fifth embodiment, the solid longrollers take a larger portion of the bearing""s loading than the hollow shortrollers, this is because of the higher stiffness and the higher resistance of the long-rollers against radial compression in comparison to the softer hollow shortrollers, the wall of which deflect somewhat during radial compression in the loaded roller bearing.
In case the load on the roller bearing is increased and the two raceways of the bearing, between which the elastic rollers run, approach each other somewhat, then the loading on the relatively stiff long-rollers become increased more rapidly than the loading on the adjacent, elastically more easily compressible short-rollers. Therefore, during increase of the roller bearing""s load the long-rollers carry a concomitantly growing part of the roller bearing""s load. This feature brings the effect, that the relatively soft short-rollers of the cage having less strength are not becoming overloaded even in case where the roller bearing carries very high bearing loads.